With BTC, the processing power of the entire cluster is used to essentially secure the monetary platform. That's why the BTC system is so difficult to "hack" or "scam." You'd need a supercomputer as powerful as the entire computing cluster in order to do so. (and at this point in time only a few distributed computing projects have that kind of power) The only other way to cheat the system is to steal virtual wallets, but technically that's not cheating the system but the individual users.

EVGA gives EVGA bucks to their folders that keep up a predetermined point production and I believe NCIX used to do point giveaways for their folding team. Aside from corporate entities doing freebies there's really no way to give virtual currency through folding. (for currency to be used and accepted there needs to be some sort of security to ensure its value)